Significance of the changes in plasma amino-acid levels in meningococcal infection

How acute and chronic physical disease may influence mental health - An Analysis of neurotransmitter precursor amino acid levels

Patients with somatic diseases are more likely to develop depression than physically healthy individuals, and comorbid depression has been shown to incrementally worsen patients´ health. Physical conditions are known to influence neurotransmitter precursor amino acids, changes in which are associated with depressive symptoms. In this prospective study we investigated neurotransmitter precursor amino acids levels in patients with acute and chronic physical disease and evaluated their association with depressive symptoms. 177 subjects with and without chronic medical comorbidity (factor: chronic physical disease) admitted to the trauma and orthopaedic surgery ward for a surgical intervention (factor: acute physical disease) were included in the analysis. Chronic medical comorbidity was scored using Charlson Index and depressive and anxiety symptoms using the Hospital Anxiety and Depression Scale (HADS, factor: mental health). The effect of covariates was also evaluated. C-reactive protein (CRP), neopterin, kynurenine/tryptophan (KYN/TRP) and phenylalanine/tyrosine (PHE/TYR) were analysed by HPLC or ELISA prior to surgery and at discharge. Mixed Model as well as correlation analyses were performed. CRP and neopterin levels were influenced by the factors "acute physical disease" (both p < 0.001) and "chronic physical disease" (p = 0.024, p = 0.001 respectively). PHE/TYR, an index of the catecholamine pathway) was related to the factors "acute physical disease" (p < 0.001) and "mental health-depression" (p = 0.012), while KYN/TRP (an index of the kynurenine pathway affecting also serotonin) was associated with "chronic physical disease" (p = 0.005). No significant effect of "mental health-anxiety" was found. The effect of "mental health-depression" on PHE/TYR was more pronounced in females (gender p = 0.003). Differences in HADS depression values correlated with changes in PHE/TYR and both correlated with CRP values. In conclusion, inflammatory reactions related to acute or chronic physical conditions can influence the availability of neurotransmitter precursor amino acids l and these changes are associated with mental health.

Elevated plasma phenylalanine in severe malaria and implications for pathophysiology of neurological complications

Cerebral malaria is associated with decreased production of nitric oxide and decreased levels of its precursor, l-arginine. Abnormal amino acid metabolism may thus be an important factor in malaria pathogenesis. We sought to determine if other amino acid abnormalities are associated with disease severity in falciparum malaria. Subjects were enrolled in Dar es Salaam, Tanzania (children) (n = 126), and Papua, Indonesia (adults) (n = 156), in two separate studies. Plasma samples were collected from subjects with WHO-defined cerebral malaria (children), all forms of severe malaria (adults), and uncomplicated malaria (children and adults). Healthy children and adults without fever or illness served as controls. Plasma amino acids were measured using reverse-phase high-performance liquid chromatography with fluorescence detection. Several plasma amino acids were significantly lower in the clinical malaria groups than in healthy controls. Despite the differences, phenylalanine was the only amino acid with mean levels outside the normal range (40 to 84 microM) and was markedly elevated in children with cerebral malaria (median [95% confidence interval], 163 [134 to 193] microM; P < 0.0001) and adults with all forms of severe malaria (median [95% confidence interval], 129 [111 to 155] microM; P < 0.0001). In adults who survived severe malaria, phenylalanine levels returned to normal, with clinical improvement (P = 0.0002). Maintenance of plasma phenylalanine homeostasis is disrupted in severe malaria, leading to significant hyperphenylalaninemia. This is likely a result of an acquired abnormality in the function of the liver enzyme phenylalanine hydroxylase. Determination of the mechanism of this abnormality may contribute to the understanding of neurological complications in malaria.

Amino acid profile and nitric oxide pathway in patients on continuous ambulatory peritoneal dialysis: L-arginine depletion in acute peritonitis

To gain insights into the amino acid metabolism and L-arginine-nitric oxide system, we studied 21 control continuous peritoneal dialysis (CPD) patients and 13 patients with 15 episodes of acute peritonitis. The concentrations of amino acids, including L-arginine, were measured in the peritoneal dialysate and in the serum. The data demonstrate that patients with end-stage renal disease on CPD who have acute peritonitis develop L-arginine deficiency. The majority of patients with acute bacterial peritonitis have increased nitric oxide production as judged by the level of nitrites in the dialysate. The recovery from peritonitis is associated with a decline in nitric oxide generation. Paradoxically, there is a smaller subgroup of these patients that shows low nitrite levels during acute peritonitis. The nitrite to L-arginine ratio in the peritoneal dialysate is increased in patients with peritonitis, further suggesting the development of substrate deficiency. These findings implicate L-arginine as a conditionally essential amino acid in CPD patients with acute peritonitis and raise questions concerning the necessity of L-arginine supplementation.